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  • 1.
    Pourbafrani, M.
    et al.
    University of Borås, School of Engineering.
    Talebnia, Farid
    University of Borås, School of Engineering.
    Niklasson, C.
    Taherzadeh, M.J.
    University of Borås, School of Engineering.
    Protective Effect of Encapsulation in Fermentation of Limonene-contained Media and Orange Peel Hydrolyzate2007In: International Journal of Molecular Sciences, ISSN 1422-0067, E-ISSN 1422-0067, Vol. 8, no 8, p. 777-787Article in journal (Refereed)
    Abstract [en]

    This work deals with application of encapsulation technology to eliminate inhibition of D-limonene in fermentation of orange wastes to ethanol. Orange peel was enzymatically hydrolyzed with cellulase and pectinase. However fermentation of the released sugars in this hydrolyzate by freely suspended S. cerevisiae failed due to inhibition of limonene. On the other hand, encapsulation of S. cerevisiae in alginate membranes was a powerful tool to eliminate inhibition of limonene. The encapsulated cells were able to ferment the orange peel hydrolyzate in 7 h, and produce ethanol with yield 0.44 g/g fermentable sugars. Cultivation of the encapsulated yeast in defined medium was successful, even in the presence of 1.5% (v/v) limonene. The capsules’ membranes were selectively permeable to the sugars and the other nutrients, but not limonene. While 1% (v/v) limonene was present in the culture, its concentration inside the capsules was not more than 0.054% (v/v).

  • 2.
    Pourbafrani, Mohammad
    University of Borås, School of Engineering.
    Citrus Waste Biorefinery: Process Development, Simulation and Economic Analysis2010Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The production of ethanol and other sustainable products including methane, limonene and pectin from citrus wastes (CWs) was studied in the present thesis. In the first part of the work, the CWs were hydrolyzed using enzymes – pectinase, cellulase and β-glucosidase – and the hydrolyzate was fermented using encapsulated yeasts in the presence of the inhibitor compound ‘limonene’. However, the application of encapsulated cells may be hampered by the high price of encapsulation, enzymes and the low stability of capsules’ membrane at high shear stresses. Therefore, a process based on dilute-acid hydrolysis of CWs was developed. The limonene of the CWs was effectively removed through flashing of the hydrolyzate into an expansion tank. The sugars present in the hydrolyzate were converted to ethanol using a flocculating yeast strain. Then ethanol was distilled and the stillage and the remaining solid materials of the hydrolyzed CWs were anaerobically digested to obtain methane. The soluble pectin content of hydrolyzate can be precipitated using the produced ethanol. One ton of CWs with 20% dry weight resulted in 39.64 l ethanol, 45 m3 methane, 8.9 l limonene, and 38.8 kg pectin. The feasibility of the process depends on the transportation cost and the capacity of CW. For example, the total cost of ethanol with a capacity of 100,000 tons CW/year was 0.91 USD/L, assuming 10 USD/ton handling and transportation cost of CW to the plant. Changing the plant capacity from 25,000 to 400,000 tons CW per year results in reducing ethanol costs from 2.55 to 0.46 USD/L in an economically feasible process. Since this process employs a flocculating yeast strain, the major concern in design of the bioreactor is the sedimentation of yeast flocs. The size of flocs is a function of sugar concentration, time and flow. A CFD model of bioreactor was developed to predict the sedimentation of flocs and the effect of flow on distribution of flocs. The CFD model predicted that the flocs sediment when they are larger than 180 micrometer. The developed CFD model can be used in design and scale-up of the bioreactor. For the plants with low CW capacity, a steam explosion process was employed to eliminate limonene and the treated CW was used in a digestion plant to produce methane. The required cost of this pretreatment was about 0.90 million dollars for 10,000 tons/year of CWs.

  • 3.
    Pourbafrani, Mohammad
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Forgacs, Gergely
    University of Borås, Faculty of Textiles, Engineering and Business.
    Sárvári Horváth, Ilona
    University of Borås, Faculty of Textiles, Engineering and Business.
    Taherzadeh, Mohammad J.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Framställning av mångahanda biprodukter från fasta citrusrester2011Patent (Other (popular science, discussion, etc.))
  • 4.
    Pourbafrani, Mohammad
    et al.
    University of Borås, School of Engineering.
    Taherzadeh, Mohammad
    University of Borås, School of Engineering.
    Ethanol from Softwood: Process Simulation and Energy Analysis2009Conference paper (Other academic)
  • 5.
    Pourbafrani, Mohammad
    et al.
    University of Borås, School of Engineering.
    Talebnia, Farid
    University of Borås, School of Engineering.
    Taherzadeh, Mohammad
    University of Borås, School of Engineering.
    Production of Bioethanol from Citrus Wastes by Encapsulated Yeast2009In: Proceeding ISWA/APESB 2009 World Congress, Lissabon, Proceeding ISWA/APESB 2009 World Congress , 2009Conference paper (Refereed)
  • 6.
    Talebnia, Farid
    et al.
    University of Borås, School of Engineering.
    Pourbafrani, Mohammad
    University of Borås, School of Engineering.
    Taherzadeh, Mohammad J.
    University of Borås, School of Engineering.
    Lundin, Magnus
    University of Borås, School of Engineering.
    Optimization study of citrus wastes Saccharification by dilute acid hydrolysis2008In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 3, no 1, p. 108-122Article in journal (Refereed)
    Abstract [en]

    Optimization study of citrus wastes Saccharification by dilute acid hydrolysis

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